In various printing technologies, marking material is applied to the surface of an intermediate imaging element, such as a belt or a drum. The print media to which the image is ultimately to be applied (such as paper) is then pressed against the intermediate imaging element to transfer the image from the intermediate imaging element to the print media. In one example using electrostatographic or xerographic printing, an image of ink (liquid or dry toner) is formed on an electrically charged image receptor. The print media is pressed against the image receptor to transfer the image to the print media. The image is subsequently fused to the print media by applying pressure with a fuser roller. In another example using phase change ink jet printing, ink is deposited to form an image on the surface of an imaging drum. A transfix roller presses the print media against the image-bearing drum surface to transfer the ink image from the drum surface to the print media and fuse the ink image to the print media.
In many circumstances, it is desirable for the pressure applied to be constant, regardless of the thickness of the print medium. Therefore, displacement of the pressure applicator due to different thicknesses of print medium should not materially change the magnitude of the pressure applied. Furthermore, it is often desirable that the pressure applied be balanced across the width of the print medium.
In accordance with an aspect of the present invention, an image transfer mechanism for a printer having an imaging element includes a transfer roller having a rotational axis, and a transfer lever mechanism attached to the transfer roller for selectively urging the transfer roller against the printer imaging element. The transfer lever mechanism provides the transfer roller translational freedom of movement in at least one direction substantially perpendicular to the rotational axis of the transfer roller. A load mechanism attached to the transfer lever mechanism for applying a load force to the transfer roller when the transfer roller engages print media positioned between the imaging element and the transfer roller. Portions of the load mechanism can be placed somewhat away from the transfer roller, in positions in which more space may be available within the printer.
In accordance with another aspect of the present invention, an image transfer mechanism for a printer having a printer frame and an imaging drum attached to the printer frame includes a roller arm having a proximal end and a distal end, a transfer roller having a longitudinal axis, and a load arm having a proximal end and a distal end. The axis of the transfer roller is rotatably attached to the roller arm. The proximal end of the roller arm is attached to the load arm between the proximal end and the distal end of the load arm. The proximal end of the load arm is pivotally attached to the printer frame, and a load mechanism for applying a load force to the distal end of the load arm urges the load arm toward the imaging drum. An engaging mechanism selectively urges the distal end of the roller arm toward the imaging drum.